I was always told that maintanance sprays (like WD 40) are for water displacement (the WD in WD 40 stands for water displacement) and have no real lubricating property's.
As said that is what was drilled into me when I was on the spanners. (grease monkey for 10 years servicing buses, the amount of times the management and stores thought the maintainance sprays were the same as spray grease was unreal)
A few weeks ago a chap at my gun club came in with a BP pistol, to his horror the pistol had rusted solid, other BP shooters spent 20 mins knocking out the cylinder ram/spindle, I commented that the pistol had never seen any oil, the owner said "I cleaned it like normal in hot soapy water, rinse in boiling water, leave it on some cloth to dry out as it cools, wipe it down to make sure its dry, then give it a good spray with WD"
It was the discussion about real oil v sprays that convinced him that a cheap gun oil is better than any spray, when I told him about the Napier oil (with vapour release that attaches to any metal surface and prevents rusting) as soon as he finished with his other BP pistol he went to the local gun shop to buy some.